Seattle weather: Summer saves its hottest breath for last

In the Northwest, we are fond of saying that September is often the best month of the summer. But this — this is beyond all expectations.

We’ll spare you all the scientific explanations for why our current warm streak is happening, but rest assured that it’s about to become historic. The record for most consecutive September days with a high temperature 80 degrees or warmer is eight, set in 1989, and we hit seven straight Friday with the mercury climbing as high as 85. These are the warmest temperatures of the year; we were never higher than 77 in all of July and August.

Remember this? It's from last year's Bumbershoot. You can thumb your nose at it now. (Joshua Trujillo, Seattlepi.com)

Forecasters are calling not just for a continuation of this brilliance into at least the early part of next week, but a warm-up that could have us scraping 90 on Sunday. The warm weekend should give us nine straight days of 80 or better. And this from a city that couldn’t even reach 70 this year until May 20.

The high temperatures of the past week have been about 10 degrees warmer than normal.

The big question then will be — how long can it last? KOMO meteorologist Scott Sistek is holding out for the possibility of another 90-degree day Monday. This goes against the grain of computer models that show the warm air mass moving east by then, but Sistek’s experience locally tells him the computers are usually too quick to resolve these situations.

For something completely different on this warm spell, check out UW professor Cliff Mass’ exploration of the greater difference between the high and low temperatures at this time of year. You can probably guess why this happens, but the size of the difference in some locales lately has been startling. There’s also a discussion of the effect this difference might have on the vintners in this region and their grapes!

Once it does cool down, the next issue will be rain. The National Weather Service sees none on the horizon through the end of next week, with the warm spell transitioning to cloudy/foggy mornings and sunny afternoons/evenings. There’s been no measurable rain of any real significance since Aug. 22, when .12 of an inch fell at Sea-Tac International Airport, and none before that since July 25.